Occasionally a key repeats although I do not press the key. I would like to prevent this phenomenon.

The phenomenon happens when I am pressing Ctrl+w again and again. After several times of Ctrl+w, w is inserted repeatedly without pressing any key. I have checked that this happens on several applications: firefox, konqueror, KWrite, emacs23. The same phenomenon happens with Ctrl+s. (I have not check other keybinds, because the phenomenon does not often happen.) Pressing any key stops this phenomena. If I disable the keyboard repeat by configuring System Settings for KDE, then the phenomenon seems not to happen. But I do not want to do.

Could anyone possibly tell me how to prevent this unexpected phenomenon?

My PC is Dell Dell Latitude E6220. I am working with KDE 4.6.4 on Vine Linux. I have swapped Ctrl and Caps Lock. If more information is needed, let me know.